Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.50	4.532%	$45.4714	$45.47	$45.45	$45.50
Purchase #2	$233.68	10.361%	$257.8916	$257.89	$257.90	$257.90
Purchase #3	$241.74	7.381%	$259.5828	$259.58	$259.60	$259.60
Purchase #4	$177.47	7.789%	$191.2931	$191.29	$191.30	$191.30
Purchase #5	$79.90	13.289%	$90.5179	$90.52	$90.50	$90.50
Purchase #6	$206.26	10.786%	$228.5072	$228.51	$228.50	$228.50
Purchase #7	$62.57	12.856%	$70.614	$70.61	$70.60	$70.60
7 purchase totals =	$1,045.12		$1,143.8780	$1,143.87	$1,143.85	$1,143.90